Lab-Grown Diamond Polish and Symmetry Guide (2026)

Polish and symmetry describe how well a diamond was finished after cutting. They appear together on grading reports, but they measure different things: polish covers the condition of each facet's surface, while symmetry covers the precision and alignment of the facets.

Both can affect appearance, yet neither should distract you from the complete diamond. Our usual starting point is Excellent or Very Good for both. Then compare cut quality, proportions, video, measurements and price. Excellent polish and symmetry are common in today's lab-grown inventory, so buyers rarely need to accept a poor finish to stay within budget.

We assess these grades alongside the diamond's report, magnified video, proportions and price. Our buying guidance also draws on the diamonds and jewelry Klaus and Juli have purchased, returned and inspected in stores. In practice, the report is better at identifying subtle finish features than an enlarged seller image viewed in isolation.

Lab diamond polish

Lab diamond polish describes the condition of a diamond's facet surfaces after cutting and polishing. A cutter places and finishes the facets against a rotating wheel, or scaife, charged with diamond powder.

A well-polished lab-created diamond will have minimal blemishes (external imperfections), such as scratches, nicks, abrasions, pits, lizard skin, or burn marks. These imperfections can impact the overall beauty and brilliance of the stone but do not necessarily indicate poor cutting skills (though some can be cut away).

How are lab diamonds polished?

To achieve an Excellent polish, a skilled cutter uses fine diamond abrasive to create smooth, flat facet surfaces and clean junctions. The aim is to remove polishing marks without changing the intended facet shape or proportions.

Common external imperfections found in diamonds

• Natural: Small portions of unpolished rough diamond left on the finished stone.
• Pits: Tiny openings that remain at the surface after polishing.
• Burn marks: Cloudy or whitish areas caused by excessive heat during polishing.
• Lizard Skin: An uneven texture resembling reptile scales caused by irregularities in the crystalline structure.
• Abrasion: Scratches or scuffs along facet junctions due to contact with other diamonds or surfaces during cutting, polishing, or wear.

Evaluating lab diamond polish grades

The polish grade records how noticeable the surface features are and how much they affect appearance. Gemologists assess them under controlled conditions and magnification.

GIA and IGI report polish on a scale from Excellent to Poor. The grade is based on professional examination at 10× magnification; shoppers do not need to reproduce that assessment at home.

For a larger center diamond, choose an independent laboratory report and check its finish information alongside the seller’s specifications. Report formats differ: IGI and earlier GIA reports give individual grades, while GIA’s current D–Z lab-grown assessments group quality as Premium or Standard. Our grading and certification guide explains the difference.

GIA grading system for polish

1. Excellent: The highest polish grade, with no or insignificant polish features at 10× magnification.
2. Very Good: Minor polish features visible under examination at 10×, usually not visible to the unaided eye.
3. Good: More noticeable polish features at 10×. Inspect their effect on the diamond’s appearance.
4. Fair: Polish features are obvious at 10× and may affect appearance or durability.
5. Poor: Severe polishing features are readily visible and can significantly detract from appearance.

How does lab diamond polish affect brilliance?

Severe polish features can interfere with light at the facet surface and reduce the crispness of reflections. The difference between Excellent and Very Good polish is usually far less important than the diamond's overall cut, proportions and transparency.

Can you see diamond polish with the naked eye?

Usually not. Most shoppers will not see the difference between Excellent and Very Good polish without magnification. Fair or Poor polish can be easier to notice and may affect the diamond's appearance.

The example below has a Good polish grade. Its magnified image can reveal surface features, but the grading report remains the reliable source for the finish assessment.

Example of a lab diamond with only a “good” polish grade

Polish still belongs in the comparison even when its features are not visible to the naked eye. In practice, prioritize the overall cut and face-up appearance; do not pay a large premium merely to move from Very Good to Excellent polish.

When you buy at reputable lab-grown diamond retailers, you’ll find that many diamonds have Excellent polish. But be sure to always check the grading in the certificate and under product details.

Mined vs. lab diamond polish

When it comes to diamond polish, there is no difference between a mined and a lab-grown diamond. Both types of diamonds undergo the same polishing process to achieve their final shape and appearance.

Lab diamond symmetry

Lab diamond symmetry refers to the precision of a diamond’s surface features and overall diamond shape. It takes into account things like facet alignment, table size, girdle thickness, and culet placement. When these elements are well-proportioned and aligned correctly, they create symmetrical patterns that allow light to reflect evenly throughout the stone.

A higher symmetry rating means that the facets and outline are more precisely aligned. Symmetry supports an orderly light pattern, although the complete cut—not the symmetry grade alone—determines brilliance.

What is the difference between lab diamond symmetry and cut?

Cut and symmetry are related but distinct. For round brilliants, the overall cut grade considers face-up appearance, proportions and craftsmanship. Symmetry focuses more narrowly on facet alignment and the precision of the outline. A strong symmetry grade supports an orderly pattern, but it does not guarantee exceptional sparkle by itself.

Can you see diamond symmetry with the naked eye?

Minor symmetry features are difficult to see without magnification. More serious asymmetry can affect the outline or light pattern and may create uneven dark areas.

Here are examples of lab-grown diamonds with Good and Very Good symmetry grades. Even in a magnified diagram, the difference can be difficult for an untrained buyer to spot.

Example of a lab diamond with a “good” symmetry grading (from Ritani)

Example of a lab diamond with a “very good” symmetry grading (from Ritani)

Why lab diamond symmetry is important

When shopping for lab-grown diamonds or lab-grown diamond jewelry, be sure to pay attention to the symmetry grade listed on their grading report. Look for diamonds that have been graded “excellent” or at least “very good”. It’s also essential to buy from reputable dealers who provide accurate certification as proof of what you are buying.

The benefits of a diamond with a high symmetry grading are:

• Better light performance: Diamonds with good symmetry grades have better fire (flashes of color) and scintillation (sparkles) due to their ability to reflect more light back out through their top surfaces resulting in increased brightness levels.
• A more orderly pattern: Precisely aligned facets support a balanced face-up pattern.
• Cut quality: Symmetry also plays a role in the cut quality of your diamond, which is one of the most important factors in determining its overall beauty. A well-cut diamond with good symmetry will have maximum brilliance and fire.

Diamond symmetry categories

Diamond symmetry refers to the precision of a diamond's facets and outline. A highly symmetrical diamond has accurately aligned facets and a balanced pattern, but the symmetry grade does not mean every proportion is automatically ideal.

Lab diamond symmetry assessment is divided into two categories:

1. Proportion-related assessments focus on how well each facet aligns with its corresponding opposite facet.
2. Facets-related assessments evaluate the shape consistency among similar facets within individual diamonds.

Proportions-related lab diamond symmetry

Proportion-related lab diamond symmetry refers to the precise alignment of a diamond’s facets. A higher symmetry rating indicates that the diamond cutter has skillfully shaped and positioned each facet for optimal light performance. Conversely, asymmetrical diamonds may exhibit poor light reflection or refraction, diminishing their overall beauty.

• Misaligned table/culet: The top and bottom of the diamond are not perfectly aligned.
• Crown/pavilion angle variations: Inconsistencies in angles can affect a diamond’s brilliance.
• Girdle thickness variation: Uneven thickness can affect appearance and, at extremes, durability.

Facets-related lab diamond symmetry

Facets-related lab diamond symmetry evaluates the consistency in shape, size, and arrangement of a diamond’s facets. Diamonds with good symmetry will have uniformity across all similar facets, while those with poor symmetry might display irregularities such as extra or missing facets.

• Azimuth shift: Facets deviating from their intended positions around the stone’s circumference.
• Tilted table/facets: Facets that are not parallel to the table or other corresponding facets.
• Non-pointing: Facets that do not meet at a precise point, creating an uneven appearance.

Lab diamond symmetry grades

Like polish grades, lab diamond symmetry grades range from Excellent (Ex) to Poor (Pr), and the grading was created by GIA and is followed by other institutes such as IGI.

• Excellent: No or insignificant symmetry deviations at 10× magnification.
• Very Good: At 10x magnification, slight symmetry imperfections can be seen.
• Good: At a magnification of 10x, symmetry defects can be observed but may be acceptable.
• Fair: At 10x magnification, symmetry defects are easily noticeable.
• Poor: At a magnification of 10x, symmetry defects can be easily seen — sometimes even without magnification.

Here’s an example of a GIA lab diamond grading report showing the diamond’s symmetry grade.

Lab diamond symmetry grade shown in a diamond grading report from GIA (Brilliant Earth)

Mined vs. lab diamond symmetry

As was the case for lab diamond polish, there is also no difference between a mined diamond and a lab-grown diamond symmetry. Both types of diamonds are cut using similar techniques by skilled craftsmen who use advanced technology like lasers and computer software to achieve precise cuts and aim for perfect symmetry.

Lab diamond polish and symmetry vs. the diamond 4Cs

You may already have heard about the diamond 4Cs, which are the key diamond quality factors that are assessed by grading institutes and jewelers. The diamond 4Cs are precisely the same for mined and lab-grown diamonds since mined and lab-grown diamonds are the same, except for the origin.

The (lab) diamond 4Cs are:

• Cut quality: Cut has the greatest effect on a round diamond's brightness, fire and scintillation.
• Clarity: Clarity describes inclusions and blemishes, including their size, position and effect on the diamond.
• Color: The D-to-Z scale describes the absence or presence of body color. Color grade and light performance are separate qualities.
• Carat weight: Carat measures weight. Face-up dimensions determine how large the diamond looks.

So what’s more important? Lab diamond polish and symmetry or the diamond 4Cs?

Balance cut, clarity, color, carat weight, measurements and price. Excellent polish and symmetry are worthwhile when the price is competitive, but they should not come at the expense of cut quality or an attractive face-up appearance. We normally stay at Very Good or better for both; current lab-grown inventories make that an easy starting point.

What are Triple Ex lab diamonds?

Triple-Ex lab diamonds are those with an excellent cut grade as well as excellent polish and symmetry, hence the 3 Ex(cellent). Broadly speaking, symmetry and polish are not as crucial as diamond cut quality and sometimes not as critical as clarity and color.

That said, polish and symmetry still affect a diamond's finish and appearance. There is usually no need to compromise heavily on either grade: lab-grown inventories contain many Excellent and Very Good options, and our 2026 lab-grown versus mined price comparison shows why buyers can often improve specifications while remaining within budget.

What are super ideal diamonds?

Some sellers use labels such as “super ideal” or “hearts and arrows” for selected round diamonds. Treat these as collection labels, not independent grades. Confirm the grading report, proportions and optical pattern for the individual stone.

However, they can be expensive, and sometimes you can find lab diamonds with “only” ideal cut grades that can be just as good. So make sure to study the diamond images closely.

Tips for buying lab diamonds with excellent polish and symmetry?

Online jewelers usually offer broader inventories and easier price comparison. A showroom can add value when you want to compare diamonds or settings in person. Whichever route you choose, look for the individual grading report, useful magnified video, complete pricing and practical return terms.

Tips for choosing a trustworthy lab diamond jeweler

1. Independent grading: Choose a report from a recognized laboratory and read the actual document. IGI reports provide individual quality grades; current GIA D–Z lab-grown assessments use Premium or Standard. Check the finish information, measurements and weight rather than assuming every report uses the same format.
2. Useful inspection tools: Look for a clear 360-degree video, full measurements and an accessible report before buying.
3. Return policy and warranty: Read the actual terms, including the return period, exclusions, shipping responsibility and whether a resized or custom ring remains returnable.

Where to buy lab diamonds with excellent polish and symmetry

Most large lab-grown diamond inventories let you filter by polish and symmetry. Start with Excellent or Very Good, then compare cut, proportions, video and total price. These jewelers have different strengths:

GIA grades polish and symmetry from Excellent to Poor at 10× magnification. For round brilliants, these finish assessments contribute to the overall cut grade, but a Very Good finish can still occur on a top-cut diamond. See how GIA grades diamonds and its current polish and symmetry feature guide.

Lab diamond polish and symmetry FAQ

How important are symmetry and polish in a lab diamond?

Symmetry and polish are crucial for a lab diamond’s light performance, enhancing its brilliance, fire, and scintillation. While not as significant as cut quality, they contribute to the overall beauty of the stone. High-quality symmetry ensures proper facet alignment and proportions, while excellent polish minimizes surface imperfections.

How does symmetry affect lab diamonds?

Symmetry affects a diamond’s ability to reflect light efficiently by ensuring that facets align properly and proportions are symmetrical. Misaligned or uneven facets can cause light leakage or distortion, diminishing the stone’s sparkle and visual appeal. A well-proportioned symmetrical lab diamond maximizes light return for optimal brilliance.

What is the importance of polish in lab diamonds?

A high-quality polish eliminates microscopic blemishes on facet surfaces, which could disrupt light reflection within lab-grown diamonds. Excellent polish gives facet surfaces a cleaner finish. It does not change the diamond’s clarity grade.

Conclusion

Understanding lab diamond polish and symmetry is crucial when shopping for lab-grown diamonds. A high-quality polish enhances a diamond’s sparkle, while symmetry maximizes its light performance. The GIA grading methodology helps assess the quality of both factors, and it’s essential to examine your own lab-grown diamond before making a purchase.

When buying diamonds, it is essential to look for both good symmetry and polish features. In addition, it’s always best to buy from reputable jewelers who can provide you with diamond grading reports that include detailed information about the diamond’s cut, carat weight, clarity, color grade, and other important characteristics.